1. Field of the Invention
The present invention relates to methods and system of dynamically managing end-to-end network loss during a phone call.
2. Background Art
FIG. 1 illustrates a fixed-loss system 10 configured to facilitate execution of a phone call between an endpoint 12 of a calling party and an endpoint 14 of a called party where signals are exchanged in a send and receive direction 16, 18 over a network 20. Each time the signals travel from one endpoint 12 to the other 14, a certain amount of loss may be added to the imparted signals to reduce the annoyance caused by echo. This may be done since the primary (non-echoed) audio is attenuated once, whereas the returned echo is attenuated twice (once from talker to listener, and once more from listener back to talker). The loss may also be imparted to reduce signal strength in a manner that facilitates volume control. The loss may also be imparted to control saturation levels and other operating characteristics associated with the phone call. Regardless of the motivation for inserting the loss and the amount of loss inserted, the loss is commonly referred to as end-to-end loss as it represents the amount of loss experienced by signals traveling from one endpoint 12 to the other 14.
Knowing the amount of end-to-end loss in each direction between two endpoints 12, 14 is critical to maintaining a desirable level of quality for the phone call. The amount of end-to-end loss can vary depending on a media connection and network connection. For example, the media connection, generally defined as the phone-to-ear piece connection, can introduce a certain amount of loss, while the network connection, generally defined as the encode-to-decode connection used to carry signaling between the media connections, can introduce another amount of loss.
To insure adequate levels of loss are included within the network 20, the network 20 may be constructed in a manner that fixes the introduced losses at a particular loss value for all phone calls having endpoints 12, 14 within the same network 20. This insures end-to-end loss is proper when both endpoints 12, 14 are on the same network 20, typically by configuring each endpoint to introduce a fixed amount of loss. As illustrated, each of the endpoints introduces −3 dB of loss in both of the send and receive directions 16, 18 such that the total end-to-end loss is −6 dB in each direction 16, 18. (Necessarily, the communications mediums and mechanisms induce additional loss.) The endpoint 12, 14 or devices connected to it may be configured to operate most desirably when the total amount of loss is the same in both directions 16, 18.
While the fixed introduction of −3 db of loss is helpful with respect to calls having endpoints within the same network 20, the fixed loss strategy becomes problematic in maintaining the same amount of loss in both directions 16, 18 if one of the endpoints 12, 14 is outside the network of the other endpoint. FIG. 2 illustrates an inter-network system 30 where execution of a phone call between first and second endpoints 32, 34 requires signals to be carried over first and second networks 36, 38. The first network 36 is shown to operate at an end-to-end loss of −6 dB with the introduction of −3 dB of loss in both of a send and a receive direction 40, 42 while the second network is configured to operate at an end-to-end loss of −4 dB with the introduction of −2 dB of loss in both of the send and receive direction 40, 42.
This inter-network scenario causes sound levels at the first endpoint 32 to be softer than the desired level and at the second endpoint 34 to be louder than the desired level. This type of signal level discrepancy can lead to a number of issues. For example, echo may become an issue if the lower than desired loss at the first endpoint 32 is below that which is required by the first network configuration to eliminate echo. Saturation may become an issue if the stronger than desired loss at the second endpoint 34 causes voice transmissions to interfere with other transmissions, e.g. data. Volume control may become an issue if the lower than desired loss at the first endpoint 32 causes the second endpoint 34 to sound overly quiet.
The fixed-loss configuration shown in FIG. 1 is suitable for endpoints 12, 14 within the first network 20. The inability of the first network 20 to introduce other amounts of loss becomes problematic when one of the endpoints is on a network configured to operate at different loss levels, as described with respect to the inter-network configuration shown in FIG. 2.